Well the good news (from my previous post) is that the car is running or should I say, was running. We purchased a new battery and ran the car for about 30-40 miles and then the car lost all power. To say the least with all we have been through with this car, I freaked. Anyway, down to troubleshooting again. This time the problem is the alternator is not charging the battery. The car completely drained the battery so the whole trip was running off the battery only. We took the alternator to Autozone to have checked and it passed. We had the battery recharged while we were there.

From the 2carpros.com website, they say, "With the vehicle not running and the car sitting over night the battery voltage should be between 12.5 and 12.8 volts. Connect the voltage meter lead the same way you would in a battery static voltage check, Start engine (do not drive) at engine idle the voltage should be between 13.6 to 14.3 volts. If not the alternator may need replacing." I have not tested yet, but is this a good start? Are there specific fuses I need to check? Remember I am a newbie at this so please "dumb" it down for me the best you can. Any help is appreciated. The funds are starting to run low, but if you feel this is something the dealership should be able to diagnose quickly, I am for that as well. Thanks

More info as I was reading one of the post below mine. That Fuse 25, previously blew on my car as well. I did notice when I was driving the radio and interior light were not working, so I was thinking it was fuse 25 again. Would fuse 25 control the charging between the alternator and the battery?

I'm thinking you have a short. I remember mentioning checking the trunk light and the stereo to make sure they weren't shorting out on the body; was that your post I was responding to?

Could be something more than that, though. If something on that circuit was shorted and the fuse blew, that would stop the short, or so one would think.

Could be a short somewhere else.

Hmmmm... one last thing. Do you have an aftermarket radio? You might try the voltage checks you suggested with the radio in, then removing it altogether. Maybe it's hooked up wrong or has an internal short.

That post was not me (I read it though). No aftermarket radio at this time. When we were troubleshooting the ECM, is when I learned about Fuse 25 and found out how the other components were on the same fuse. This time I am just checking to see if fuse 25 would have anything to do with the alternator not charging the battery.

This post has been edited by wmacroberts: May 17 2007, 01:21 PM

We pulled the battery to check the negative battery cable ground. Sure enough when we put the new engine in it must have clipped the cable. We replaced the cable and are testing it out this weekend. One strange thing so far is that the headlights are not working and the dashboard lights. When you turn them on the time goes dim like it normally would, but there are no headlights. I checked the two fuses under the hood for the hi and low beam fuses seem ok.

Check all the fuses inside and out is all I can think of.

Have you looked at WebTech on HMAService.com? I've written up directions on how to access the information (free signup, free access) here. You can view all the schematics in the ETM section. I would check Body Electrical -> Lighting.

Good news bad news, it was an internal ignition fuse that was "browned" out. After I replaced it, the headlights and dashboard worked properly. The bad part is we drove the car around to test the fix and it drained again. I have decided at this point based on my limited experience with electrical issues to bring it in to a trusted dealership. I will let you know the final outcome and hopefully long term resolution. - Thanks

It ultimately turned out to be the alternator even though it tested out ok at AutoZone. We had it replaced and it has been running great (knock on wood) for about a week now. Thanks.

I bet they didn't fully test it. Two things can go wrong with an alternator: It can fail to produce power, or the diodes on it can short out, draining the battery when the car is off. I bet the AZ guy just checked to see if it was charging but didn't check the diodes. In my experience, the diodes are usually what fail on an alternator.

Anyway, glade you hear you're back in business!

Well, seemed as good a place as any to enter this.....

Have a 2002 Elantra GLS, AT, 75K (bought new, all maintenance done, etc.)

Out of nowhere, my mileage dropped by about 40%. Only thing I'd noticed was when starting in the morning, it'd start immediately, but when you'd go to give it gas after putting in gear (reverse), it'd have a little hesitation/sputter (pretty minimal at that), and that was it. No check engine light. I thought it might be another fuel pressure regulator (it'd been replaced before), but the symptoms weren't quite right, as it started/idled immediately.

They (Hyundai dealer) hooked it up, and it showed that the alternator was going bad/weak (the battery had been replaced late last fall and was fine). I hadn't noticed any electrical symptoms, but they showed me the test numbers and the voltages were low (not really bad, but only like 12.3v with the car running/charging. Seemed odd that there wasn't a trouble or 'check engine' light coming on, but apparently they knew what they were saying as the new alternator cleared up both the hesitation and mileage issues.

I'd never have guessed that would be the problem; has anyone had anything like that? I'd hate to think they found a detached hose or something and "sold" me an alternator as the "fix".....

You know... dealerships don't do that kind of stuff. Maybe in the "old days", sure, but it's just not good business anymore and you can't keep the doors open doing that kind of stuff. If they replaced the alternator, even showing you the test readouts, then yes, the alternator was bad.

Well, that's what I would tend to think as well; as I said, it just seemed like odd symptoms for what ended up being wrong, that's why I asked if anyone else had heard of problems of a similar nature. BTW the extent of what they showed me were the loaded and unloaded charging voltages before and after replacing the alternator. And as I'd said, I had no other "low charge" or "low voltage" symptoms (headlight dimming when the A/C or fan was turned on, etc.), no check engine light, no "voltage" warning light.

My headlights are dimming when I roll my windows/ sunroof up and hold the switch too long. I can push the window switch on all 4 windows at once, but as soon as one of the 4 is fully up the other 3 slow down and the headlights dim. Is this a low voltage problem or is it normal?

2003 Elantra gt 86000 miles

Same here with lights. It's normal because window motor drains less power while moving than in holding position where it drains a lot more. I do not recommend pushing the motor even though the window is fully opened/closed. Motor can hold out but a sprocket or a bearer could be broken - had my share of experience so to say... Hope this helps.


cheers!